The present invention relates to a short message system, especially a prepaid message system, for sending messages by means of mobile telephones and, where appropriate, managing a prepaid short message service, which system comprises switching arrangements on which the mobiles depend for radio connection, and short message servers at which the messages from a mobile arrive and are routed back, in the form of messages “destined for a mobile”, to the destination mobiles, the mobile sending messages including a secret code in the message, although that is not obligatory.
Short messages SMS are transmitted by mobile telephones. In a large number of cases, however, mobile telephones use the prepayment system, which does not allow the question of short messages to be handled efficiently.
The prepaid telephone card market for mobiles has been a major factor in the expansion of the mobiles market in order to avoid the problems of non-payment or to make a costly billing system more economical and simplify administration.
In some countries, all subscribers are prepaid, and some operators are abandoning post-payment completely and accepting only prepaid subscriptions.
Under these circumstances there arises the problem of the short message service which must be provided for subscribers with prepaid subscriptions, since short messages are likely to represent a very considerable proportion of an operator's activity.
There are at present three types of solution for dealing with this problem:    the intelligent network IN,    service nodes SN and    hot-billing.
The intelligent network IN uses a service control point SCP which is interrogated by service switching point software SSP of the short message services each time a subscriber wishes to make a telephone communication. The control point SCP then interrogates the credit database SDP in order to authorise the communication for a period of X seconds and interrupt it after that time.
The second solution is that of service nodes SN, which consists in routing all prepaid subscribers' communications to that dedicated switching arrangement, which manages the credit database.
Finally, hot-billing consists in creating billing tickets at the level of network switching arrangements MSC, which transmit periodically, typically every few minutes, their consumption to a debiting system for the credits that is capable of interrupting a call. However, this relatively old solution has many disadvantages owing to the risk of credit being exceeded.
In those three solutions for prepaid telephony, telephone credit can generally be topped up by the purchase of credit cards (scratch cards) which contain a concealed secret number with all security rules. That number is used to ask an interactive vocal server SVI to top up the credit by the amount of the scratch card. The various handling operations are relatively complicated. In addition, there is the cost of the interactive vocal server and that of the credit database SDP. Nevertheless, the invention can, without changing anything, also be associated with a SVI for topping up credit. In that case, the system is more convenient to use because the prepaid user does not have to add a secret code before the text.
In conclusion, the solutions hitherto employed are relatively cumbersome, not very flexible, not very reliable and are generally not suitable for small or medium-sized operators.
Among the current technical solutions envisaged and envisageable for prepaid short messages, in the case of the intelligent network IN it is not possible to interrogate a service control point SCP when a message SMS-MO transmitted by a mobile is sent.
The second theoretical solution, that of service nodes (SN), does not work since they are not requested at the time of a SMS-MO unless a special SMSC which is capable of interrogating the credit in the SN is incorporated in the SN (a solution which is not very widespread and in this case the SMSC is too simplified).
Finally, the hot-billing of SMS-MO messages is a possibility, but the billing tickets for the SMS-MO messages are sent with a considerable delay, which may reach several hours, to the database SDP containing the credit remaining for the prepaid service. Where there is insufficient credit, there is disconnection by way of an interface with the database in order to locate the subscriber on the basis of his mobile number (HLR). The disadvantage of this solution is that it requires a specially developed and costly SDP server, as well as the disadvantage that debiting is delayed according to the rate of receipt of the SMS-MO message tickets.
Certain other solutions have already been employed, for example that of the SMSC server equipped with particular software allowing the credit database SDP to be interrogated, but such solutions have been developed in closed contexts. The solution is excellent but the price of the software is very high.
Finally, another solution which is sometimes used by some large operators consists in sending all SMS-MO messages to a dedicated server SMSC which sends them, by way of a dedicated connection, to the credit management point SDP; the latter checks whether the subscriber is prepaid and whether he has credit, and then sends the message to other servers SMSC dedicated to forwarding the message to the destination mobile (SMS-MT), while the first server SMSC is dedicated to messages coming from a mobile SMS-MO with reduced means, in a flexible manner and in total security.
In that system, SMS message debits are made in real time, but the cost of the solution is relatively high and it is not suitable for small or medium-sized operators.
The object of the present invention is to develop a short message system which is, in particular, suitable for small and medium-sized operators and, especially, for those which have only prepaid subscribers, allowing prepaid short messages SMS to be managed easily.